Carburetor



Patented Sept. 14, 1954 CARBURETOR Elmer Olson, Rochester, N. Y.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Application March 23, 1951, Serial No. 217,123

9 Claims.

This invention relates to carburetors for internal combustion engines,particularly for automotive use and more specifically to the means forsupplying combustible mixture to the engine during idling and near oroff idling operation.

The primary object of the present invention is to provide means forsupplying fuel mixture for idling or near idling operation which iseifective to supply a mixture having substantially a correct fuel-airratio and will neither be too rich nor too lean in any part of the idleor near idle range. tion is embodied in a carburetor of the type shownin the copending application of Elmer Olson, Serial No. 109,347, filedAugust 9, 1949, but the invention is not designed to be applicable tothis particular carburetor only.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. 1 is a vertical section through the carburetor in which the presentinvention is embodied.

Fig. 2 is a detail section on the line 22 of Fig. 1.

Fig. 3 is a similar detail section showing a modified form of theinvention.

Referring to Fig. 1, the carburetor shown therein comprises threeseparate castings numbered I, 2 and 3, respectively. The casting l isthe carburetor outlet which is adapted to be connected with the intakemanifold in the usual manner, the casting 2 is positioned above theoutlet casting l and has a constant level fuel chamber 2a formedtherein, while the casting 3 forms a cover for the fuel chamber and alsohas the air intake 4 formed therein. These three castings are separatedby gaskets to form tight joints and to limit the transfer of heatbetween the castings as much as possible by preventing any metalliccontact of the castings with each other.

In the outlet casting l, a throttle shaft 5 is suitably journalled andsecured to such shaft is the usual throttle valve 6 which is manuallyadjustable by means not shown to control the volume of combustiblemixture which is supplied by the carburetor to the engine.

In the casting 3 a choke valve 1 is positioned and this valve is securedto a shaft 8 which is suitably mounted in the casting 3 for rotation.The choke valve in the carburetor disclosed here- As illustrated herein,the present invenin is manually operated and, when the engine isoperating at normal temperature, is adapted to be positioned in wideopen position so as not to restrict the quantity of air entering thecarburetor, but is adapted to beclosed, or partly closed, by the manualoperating connections when the engine is started cold in order tofacilitate starting, the position to which the choke valve is movedbeing dependent upon the temperature at the time of starting. The chokevalve is adapted to be moved to different positions by means of the armnumbered 9 which is adapted to be operated by a connection leading tothe dash which is not shown herein, but is of a conventionalconstruction. The arm 9 operates the choke valve through mechanism whichneed not be described herein, but is fully shown and described in thecopending application above referred to. It may be said, however, thatthe operation of the choke valve by the arm 9 is eifected through aspring I0 which holds the choke valve yieldingly closed, so that whenthe engine starts to run under its own power, the increase in enginesuction which then occurs can pull the valve open to som extent againstthe force of the spring Ill, so as to prevent overchoking.

In the carburetor shown herein, the choke valve is also designed tooperate the throttle so as to move the throttle slightly toward openposition when the choke valve is moved to its fully closed position inorder that the idling speed may be somewhat increased when the chokevalve is closed. This is done for the purpose of providing a somewhatfaster than normal idling when the choke valve is closed at lowtemperatures which is desirable to prevent stalling. The operatingconnections between the choke valve and the throttle valve. forefiecting this movement are indicated generally by the reference numeralll. Since this mechanism has nothing to do with the invention in thisapplication, it is not illustrated in detail and will not be described,but such mechanism is fully shown and described, in the aforesaidcopending application.

As already indicated, air is admitted to the carburetor through the airinlet 4 and fuel is supplied to the carburetor through a main fuelnozzle I2 which terminates at the throat of a small Venturi tube [3,which itself, terminates at the throat of a large Venturi tube l4integral with the casting 2 and forming a part of the mixture passagewhich extends vertically through the carburetor. The purpose of theseVenturi tubes is, of course, to increase the velocity of air flow pastthe end of the main fuel nozzle 12 to create a partial vacuum adjacentthe nozzle outlet in the usual and well known manner. Fuel is alsosupplied to the intake passage by an idling fuel inlet which is shown inFig. 2 and in modified form in Fig. 3. The construction of these idlingfuel inlets will be later described.

Fuel is supplied to the main and idling fuel inlets from the fuelchamber 2a and fuel is supplied to the latter through a coupling itwhich is screwed into the casting 3 and to which a fuel supply pipeextending to the main fuel tank of the vehicle is adapted to beconnected. Fuel which is supplied through the coupling [:5 enters apassage I6 formed in the casting 3 and flows through a passage in anipple 17, which is screwed in the wall of the casting 3, andcommunicates with the fuel bowl 2a when the parts are assembled as shownin Fig. l. The flow of fuel through the passage l1 into the bowl iscontrolled by a valve i8 which cooperates with the passage I1 and restson one arm of a lever [9 which is pivoted on a pin fixed in position inthe wall of the fuel chamber 2a. The lever I9 is connected to the floatmechanism which is not shown, but which is received within the chamber2a and when the fuel level in said chamber reaches a definite height,the float lifts the lever [B so as to close the valve I8 and cut oif theflow of fuel into the float chamber in the usual way. The floatmechanism is of conventional construction and has nothing to do with theinvention which is claimed in this application.

Before describing the fuel passage which conveys fuel from the floatchamber 2a to the main and idling fuel inlets, attention is called tothe fact that the carburetor is provided with an accelerator pump whichis operated manually upon sudden opening movements of the throttle toprovide a charge of fuel in addition to the fuel supplied by theordinary fuel inlet, in order to enrich the mixture for acceleration inthe usual way. The construction of this accelerator pump constitutes nopart of the present invention, but the pump includes a cylinder intowhich fuel flows from the float chamber 2a, through a passage, notshown, and slidable in the cylinder is a pump piston 26 which isoperated by a spring 2'! that is compressed when the throttle is openedsuddenly, by means of an arm 26a which is pulled downwardly when thethrottle is opened. This compression of the spring effects a delayeddownward movement of the piston 26 which takes place as the springexpands following its compression by the throttle, as the latter isopened and as the piston moves downwardly, in the manner described, itforces fuel from the space below the piston into the mixture passage tosupply the additional fuel above referred to for acceleration purposes.This pump mechanism is fully shown and described in the copendingapplication above referred to and will not be further described herein,since its construction is entirely immaterial so far as the presentinvention is concerned. A tube 28 which connects the upper end of thecylinder '25 with the carburetor intake serves as a vent for escape ofany fuel bubbles which may collect within the cylinder 25 and as a ventfor the fuel chamber 2a.

The construction which has been generally described above is the same asthat disclosed in Ser. No. 109,347 and the construction of the entirecarburetor may be the same except the means for supplying idling andpart throttle mixture which will be described in detail later. In thisapplication as well as in the earlier application the fuel conduitleading to the main and idling fuel inlets comprises three parts orpassages which together make up a conduit shaped substantially like aninverted U, one part or passage being substantially'vertical andextending downwardly into the float chamber and connecting at its upperend with a horizontal passage formed in casting 3, which, in turn,connects at its other end with a substantially vertical passage thatextends downwardly to the idling fuel inlet, the main fuel inletcommunicating with the horizontal portion of the passage substantiallymidway between its ends. As shown in Fig. 1, the fuel conduit includes avertical passage 30 formed in a member 3| which, at its upper end, issecured in any suitable way in a bore or chamber 31a formed in thecasting 3. This member, at its lower end, has a calibrated plug 32screwed into it which meters the fuel supplied to passage 30.Communicating with the chamber am is a horizontal passage 33 which, atits left end, as shown in Fig. 1, connects with a vertical passage 34which extends downwardly in the wall of the casting 2 and communicatesat its lower end with a passage 35 which leads to the idling fuel inlet,which will be later described. The passage 35 is a channel formed in thebottom of the casting 2 and connects the passage 34 with a part of theidling fuel supply passage which is formed on the casting 4 and ispositioned from passage 3d when the carburetor is assembled. Thehorizontal portion 33 of the fuel conduit is of different diameters,that part of the passage lying between the chamber 3m and the point ofconnection with the main nozzle being smaller than that part 36 of thepassage 33 which lies to the left of the main nozzle in Fig. l. A plug31 closes the left end of the passage and a tube 38 is fitted in thatpart of the fuel passage numbered 36. Such tube has a restricted opening38a at its right end and terminates somewhat to the right of thevertical passage 34. A'plurality of orifices 39 are provided immediatelyabove the main nozzle [2 to admit air for purposes of effectingatomization of the fuel and a bushing 40 having a small orifice 4|therein is positioned within the main nozzle [2 to cause a flowtherethrough at high velocity and to aid in the atomization of the fuel.This fuel passage as so far described, is of the same'construction asthat shown in the earlier application.

The fuel passage 33 delivers solid fuel to the space above the bushing40 in which it ismixed with air entering the orifices 39 and the mixturethus formed is discharged into the mixture passage through the idlingfuel supply passage, or the main nozzle I2 orboth, depending on thethrottle position. When the throttle is closed for idling the suction atthe idling fuel inlet, which connects with the mixture passage posteriorto the throttle, is so great that there is no flow from the main nozzle.As the throttle is moved toward open position the suction at'the mainnozzle is'increased while that at the idling fuel inlet is reduced, sothat during a part of the throttle movement fuel is supplied by bothinlets and as the throttle continues to move toward open position theidling fuel inlet ceases to function and all of the fuel is supplied bythe main inlet.

According to the present invention the idling fuel supply passage 35 inthe bottom" of casting 2 connects with a vertical bore 45 in the wall ofthe throttle body casting l which is located 90 circumferentially fromthe passage 34 as clearly shown in Fig. 2. The passage 45 connects atthe lower end with a diagonal passage 45 which leads to a restrictedinlet 41 connected with the mixture passage. A manually adjustable valve43 which is retained in any adjusted position by a spring 45 controlsthe inlet 41, while a plug having a passage 55 of small size therein ispositioned in the passage 45 adjacent its point of connection with thepassage 35. Formed in the wall of the throttle body casting I parallelto and adjacent the passage 45 is a bore 5| closed at its upper end bythe bottom face of the casting 2. A small passage 52 connects this borewith passage 45, while two passages 53 and 54 connect bore 5! with thecarburetor intake passage. As illustrated, the passage 54 is somewhatlarger than the passages 52 and 53 and these are shown as of about thesame size, but the drawings are not on exact scale, and the severalpassages are not shown in the drawings in their exact size. The passagesare of such sizes that the desired mixture proportions will be obtainedduring the idle and near idle range of operation.

The operation of the passages above described is as set forthhereinafter. When the throttle valve is in the fully closed or idleposition, as shown, both the passages 53 and 54 are on the anterior sideof the throttle, while the inlet 4'! is posterior to the throttle. Thehigh manifold vacuum is communicated to the opening 4'! and through thisopening to the passage 45, but the effect of this high suction on thepassage 45 is reduced by the action of the passages 52, 53 and 54 whichpermit air to flow from the mixture passage through passages 53 and 54and thence into passage 45 through passage 52. Obviously, this admissionof air reduces the suction created in passage 45 and the effect of suchsuction on the flow of fuel is still further reduced by the effect ofthe restricted opening 50. By setting the valve 48 in proper position,an idling mixture of proper proportions is obtained.

As the throttle is moved slightly toward open position for near or offidle operation, the passage 53 ceases to function as a bleed, suchpassage becoming subject to the high suction maintained posterior to thethrottle and acting to supply fuel mixture to the intake passage. Whenthis takesplace, fuel is being supplied through both the passages M and53 and the passage 53 has also become a suction passage instead of ableed. This action tends to cause the off idle mixture to become toorich, but this is prevented by the action of the orifice 5 1 whichcontinues to act as a bleed and breaks the effect of suction on passages47 and 53 sufiiciently to prevent the off idle mixture becoming too richafter the passage 53 has become a fuel supply passage.

As the throttle progressively opens, the passages 4'1 and 53 continue tosupply fuel mixture at a progressively decreasing rate due to thereduction of suction on such passages until the suction at the mainnozzle becomes so great that there is a reverse flow through thepassages 41 and 53 from the intake passage toward the main nozzle, afterwhich all of the fuel is supplied by the main nozzle alone. Before thistakes place, the main nozzle has begun to function for as alreadystated, during a part of the opening tie is closed to movement of thethrottle there is a flow of fuel from the main nozzle as well as fromthe passages 41 and 53. The passage 54 is located so far above thethrottle that it never acts as a fuel supply passage, but is always ableed.

It will be understood that the effect of the bleed hole 54 is veryslight at idling, in fact, substantially negligible because at idlingthe passage 53 is also a bleed and the passage 52 is of such small sizethat its efiect would be much the same if passage 54 were omitted, whenthe throtidling position. When the throttle begins to open, however, thebleeding action of the orifice 54 so modifies the efiect of suction,particularly on passage 55 that it is effective to prevent the mixturebecoming too rich.

It is old to employ a small orifice 53 to connect the intake passagewith a passage such as 45, in fact, such an arrangement is shown in theapplication previously referred to. With this arrangement a correctidling mixture can be obtained with proper adjustment of the valve 48,but when the throttle is slightly opened for 01f idle operation, themixture tends to become too rich. If a restriction such as 55 is put inthe passage 45, and the orifice 53 omitted, a correct idling mixturewould be still obtainable by proper adjustment of the valve 48, but theoff idling mixture would become considerably too lean. If a smallorifice 53 is used with a restriction such as 59, for the purpose ofcorrecting the leanness referred to, even if the orifice is as small asit is practical to use, the oif idle mixture tends to become too rich.By employing a bleed hole 54 of proper size, to modify the effect ofsuction on the orifice 53, the tendency to over-richness at oif idleoperation can be averted without making the mixture too lean in any partof the idle and near idle range.

While the construction and operation of a device employing therestriction 55 in addition to the orifices 54, as a means for modifyingthe mixture proportions at off idle operation, has been described andsuch construction is probably preferable for some reasons, therestriction 55 can be omitted and if the sizes of the various orificeshave the proper relation, the mixture proportions can be adequatelycontrolled without employing a restriction in the passage 45. In otherwords, if the orifice sizes are properly selected, a satisfactory resultcan be obtained without use of the restriction 55.

The construction shown in Fig. 3 is of slightly different form butfunctions in the same way as does that previously described. In thisform of the device a chamber 55 is formed in the Wall of the throttlebody casting l and a plug is positioned therein having a flange 5| ofthe same diameter as the chamber and a reduced cylindrical extension 62,between the outer wall of which and the Wall of the chamber is anannular space 53. A restricted opening 55a corresponding to the opening53 connects the passage 35 with the interior of the extension 52 andpassages 53a and 54a, corresponding to passages 53 and 54 connect thespace 53 with the intake passage, while a passage 52a connects the space53 with the interior of extension 62. The operation of this modifiedform of the device is just the same as that shown in Fig. 2 and need notbe specifically described.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form,.it is to be understood that other formsmight be adopted.

-What is claimed is as follows:

I. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling. fuelsupply passage operable to supply fuel tothe intake passage when thethrottle is open to less than a predetermined extent, a fuel conduit forconveying fuel from the fuel supply chamber to said main fuel inlet andto said idling fuel supply passage, a passage connecting the idling fuelsupply passage with the intake passage ata point posterior to thethrottle valve in all positions, a second fuel passage having arelatively' small opening connecting it with the idling fuel passage,and a plurality of passages connecting said second fuel passage withsaid intake at points anterior to the throttle valve when the latter isin closed position, said last-named passages being so positioned withrespect to the throttle valve that they progressively become posteriorto the throttle valve when said valve is moved to predetermined openpositions and one of'which supplies fuel to said intake passage.

2.- A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling fuelsupply passage operable to supply fuel tothe intake passage when thethrottle is open to less than a predetermined extent, a fuel conduit forconveying fuel from the fuel supply chamber to said main fuel inlet andto said idling fuel supply passage, a passage connecting the idlingfuel'supply passage with the intake passage at a point posterior to thethrottle valve in all positions, a second fuel passage having arelatively small opening connecting it with the idling fuel passage, aplurality of passages connecting said second fuel passage with saidintake at points anterior to the throttle valve when the latter is inclosed position, said last-named passages being so positioned withrespect to the throttle valve that they progressively become posteriorto the throttle valve when said valve is moved to predetermined openpositions, and a restriction in said idling fuel supply passage anteriorto the point of connection of any of the aforementioned passagestherewith, one of said plurality of passages being effective to supplyfuel upon a predetermined movement of the throttle.

3. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of com bustible mixturetherethrough, a main fuelinlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, a fuel conduitfor conveyii' fuel. from the fuel supply chamber to the main fuel inlet,an idling fuel supply passage operable to supply fuel to the intake whenthe throttle is open to less than a predetermined extent and connectingwith said fuel conduit at a point closely adjacent to the main fuelinlet, a passage connecting the idling fuel supply passage with theintake passage at a point posterior to the throttle valve in allpositions, and a plurality of passages connecting said idling fuelsupply passage with said intake at points anterior to the throttle valvewhen the latter is in closed position, said passages being so positionedwith respect to the throttle valve that they progressively becomeposterior to the throttle valve when said valve is moved topredetermined open positions, but one of said passages serving as a ventonly in all positions of the throttle valve.

4. A carburetor for internal combustion engines, having in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, a fuel conduitfor conveying fuel from the fuel supply chamber to the main fuel inlet,an idling fuel supply passage operable to supply fuel to the intakepassage when the throttle is open to less than a predetermined extentand connecting with said fuel conduit at a point closely adjacent to themain fuel inlet, a passage connecting the idling fuel supply passagewith the intake passage at a point posterior to the throttle valve inall positions, a second fuel supply passage connected with the firstidling fuel supply passage by a connecting passage of small sizeoperable to limit the rate of fuel flow to said second fuel supplypassage and a plurality of passages of larger size than said connectingpassage for connecting the second fuel supply passage with the mixturepassage, at points anterior to the throttle valve when the latter is inclosed position, said last-named passages being so positioned withrespect to the throttle valve that they are progressively renderedsubject to the suction maintained posterior to the throttle valve assaid valve is moved toward open position.

5. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, a fuel conduitfor conveying fuel from the fuel supply chamber to the main fuel inlet,an idling fuel supply passage operable to supply fuel to the intakepassage when the throttle is open to less than a predetermined extentand connecting with said fuel conduit at a point closely adjacent to themain fuel inlet, means for admitting air to said idling fuel supplypassage at its point of connection with said fuel conduit to formtherein a mixture of fuel and air, a passage connecting the idling fuelsupply passage with the .take passage at a point posterior to thethrottle in all positions, a second fuel supply passage connected withthe first idling fuel supply passage by a connecting passage of smallsize operable to limit the rate of fuel flow to said second fuel supplypassage and a plurality of passages of different sizes connecting saidsecond fuel supply passage with the intake passage at a point anteriorto the throttle when the latter is closed, all of said last-namedconnecting passages being of larger size than the first connectingpassage, said passages being so positioned with respect to the throttlevalve that they are progressively rendered subject to the suctionmaintained posterior to the throttle valve as said valve is moved towardopen position.

6. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling fuelsupply passage through which fuel flows when the throttle is closed oropen to less than a predetermined degree, a chamber, a flangedcylindrical element in said chamber forming an annular space betweenitself and the chamber wall, said cylindrical element communicating withthe idling fuel supply passage, a passage connecting the interior ofsaid cylindrical element with the intake passage at a point posterior tothe throttle valve, a plurality of passages connecting said annularspace with the intake passage at points anterior to the throttle valvewhen the latter is in closed position and so positioned with respect tothe throttle valve that they progressively become posterior to saidthrottle valve when it is moved to predetermined open positions, and apassage connecting said annular space with the interior of saidcylindrical element.

7. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling fuelsupply passage through which fuel flows when the throttle is closed oropen to less than a predetermined degree, a chamber, a flangedcylindrical element in said chamber forming an annular space betweenitself and the chamber wall, said cylindrical element communicating withthe idling fuel supply passage, a passage connecting the interior ofsaid cylindrical element with the intake passage at a point posterior tothe throttle valve, a plurality of passages connecting said annularspace with the intake passage at points anterior to the throttle valvewhen the latter is in closed position and so positioned with respect tothe throttle valve that they progressively become posterior to saidthrottle valve when it is moved to predetermined open positions, apassage connecting said annular space with the interior of saidcylindrical element and a restricted opening connecting the idling fuelsupply passage with said cylindrical element.

8. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling fuelsupply passage operable to supply fuel to the intake passage when thethrottle is open to less than a predetermined extent, a fuel concluitfor conveying fuel from the fuel supply chamber to said main fuel inletand to said idling fuel supply passage, a passage connecting the idlingfuel supply passage with the intake passage at a point posterior to thethrottle valve in all positions, an additional fuel passagesubstantially parallel to said idling fuel supply passage and connectedtherewith through a restricted orilice which controls the rate of fuelflow into said additional passage, a restriction in said idling fuelsupply passage anterior to and adjacent said restricted orifice, and aplurality of passages connecting said additional fuel passage and theintake passage anterior to the throttle when in closed position, saidplurality of passages being so positioned with respect to the throttlevalve that they progressively become posterior to the throttle valvewhen the throttle valve is moved to predetermined open positions.

9. A carburetor for internal combustion engines having, in combination,a constant level fuel supply chamber, an intake passage provided with athrottle valve for controlling the flow of combustible mixturetherethrough, a main fuel inlet for supplying fuel to the intake passageafter the throttle is opened to a predetermined extent, an idling fuelsupply passage operable to supply fuel to the intake passage when thethrottle is open to less than a predetermined extent, a fuel conduit forconveying fuel from the fuel supply chamber to said main fuel inlet andto said idling fuel supply passage, a passage connecting the idling fuelsupply passage with the intake passage at a point posterior to thethrottle valve in all positions, an additional fuel passagesubstantially parallel to said idling fuel supply passage and connectedtherewith through a restricted orifice, and a plurality of passages oflarger size than said restricted orifice connecting said additional fuelpassage and the intake passage anterior to said throttle valve when inclosed position, said plurality of passages being so positioned withrespect to the throttle valve that they progressively become posteriorto the throttle valve as the throttle valve is moved to predeterminedopen positions.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,895,471 Mathieu Jan. 31, 1933 2,009,280 S'prenger July 23,1935 2,035,681 Udale Mar. 31, 1936 2,987,293 Olson July 20, 19372,127,444 Emerson Aug. 16, 1938 2,215,683 Wirth Sept. 24, 1940

